In one aspect, the present invention relates to compounds which are potent inhibitors of thrombin. In another aspect, the present invention relates to novel peptide analogs, their pharmaceutically acceptable salts, and pharmaceutically acceptable compositions thereof, which are useful as potent inhibitors of blood coagulation in vitro and in vivo in mammals. In yet another aspect, the invention relates to methods of using these inhibitors as therapeutic agents for disease states in mammals characterized by abnormal thrombosis. In a further aspect, the present invention relates to methods of using these inhibitors as in vitro diagnostic agents.
Normal hemostasis is the result of a complex balance between the processes of clot formation (blood coagulation) and clot dissolution (fibrinolysis). The complex interactions between blood cells, specific plasma proteins and the vascular surface, maintain the fluidity of blood unless injury occurs. Damage to the endothelial barrier lining the vascular wall exposes underlying tissue to these blood components. This in turn triggers a series of biochemical reactions altering the hemostatic balance in favor of blood coagulation which can either result in the desired formation of a hemostatic plug stemming the loss of blood or the undesirable formation of an occlusive intravascular thrombus resulting in reduced or complete lack of blood flow to the affected-organ.
The blood coagulation response is the culmination of a series of amplified reactions in which several specific zymogens of serine proteases in plasma are activated by limited proteolysis. Nemerson, Y. and Nossel, H. L., Ann. Rev. Med., 33: 479 (1982). This series of reactions results in the formation of an insoluble fibrin matrix composed of fibrin and cellular components which is required for the stabilization of the primary hemostatic plug or thrombus. The initiation and propagation of the proteolytic activation reactions occurs through a series of amplified pathways which are localized to membranous surfaces at the site of vascular injury (Mann, K. G., Nesheim, M. E., Church, W. R., Haley, P. and Krishnaswamy, S. (1990) Blood 76: 1-16. and Lawson, J. H., Kalafatis, M., Stram, S., and Mann, K. G. (1994) J. Biol. Chem. 269: 23357-23366).
These pathways are highly inter-dependent and converge in the formation of the serine protease, Factor Xa. Factor Xa catalyzes the penultimate step in the blood coagulation cascade which is the formation of the serine protease thrombin. This step occurs following the assembly of the prothrombinase complex which is composed of factor Xa, the non-enzymatic co-factor Va, and the substrate prothrombin assembled on the surface of adhered, activated platelets or systemically circulating membranous microparticles.
Proteolytic activation of zymogen factor X to its catalytically active form, factor Xa, can occur by either the intrinsic or extrinsic coagulation pathways.
The intrinsic pathway is referred to as xe2x80x9cintrinsicxe2x80x9d because everything needed for clotting is in the blood. Saito, H., xe2x80x9cNormal Hemostatic mechanismsxe2x80x9d, Disorders of Hemostasis, pp. 27-29, Grune and Stratton, Inc. (O. D. Ratnoff, M. D. and C. D. Forbes, M. D. edit. 1984). This pathway is comprised of the zymogen serine proteases, factors IX and XI, and the non-enzymatic co-factor, factor VIII. The initiation of the intrinsic pathway results in the activation of factor XI to XIa. Factor XIa catalyzes the activation of factor IX to factor IXa which in combination with the activated form of factor VIII on an appropriate phospholipid surface, results in the formation of the tenase complex. This complex also catalyzes the formation of the serine protease, factor Xa, from its zymogen, factor X which subsequently results in clot formation.
The extrinsic pathway is referred to as xe2x80x9cextrinsicxe2x80x9d because the tissue factor which binds to and facilitates the activation of factor VII comes from outside the blood. Saito, id. The major components of this pathway are the zymogen serine protease, factor VII, and the membrane bound protein, tissue factor. The latter serves as the requisite non-enzymatic co-factor for this enzyme. The initiation of this pathway is thought to be an autocatalytic event resulting from the activation of zymogen factor VII by trace levels of activated factor VII (factor VIIa), both of which are bound to newly exposed tissue factor on membrane surfaces at sites of vascular damage. The factor VIIa/tissue factor complex directly catalyzes the formation of the serine protease, factor Xa, from its zymogen, factor X. Exposure of blood to injured tissue initiates blood clotting by the extrinsic pathway.
The formation of thrombin is catalyzed by factor Xa following the assembly of the catalytic prothrombinase complex as reviewed by Mann, K. G. et al., xe2x80x9cSurface-Dependent Reactions of the Vitamin K-Dependent Enzyme Complexes,xe2x80x9d Blood, 76:1-16 (1990). This complex is composed of factor Xa, the non-enzymatic co-factor Va and the substrate prothrombin all assembled on an appropriate phospholipid surface. The requirement of a macromolecular complex for efficient catalysis results in the protection of factor Xa from natural anticoagulant mechanisms such as heparin-antithrombin III mediated inhibition. Teite, J. M. and Rosenberg, R. D., xe2x80x9cProtection of Factor Xa from neutralization by the heparin-antithrombin complexxe2x80x9d, J. Clin. Invest., 71:1383-1391 (1983). In addition, sequestration of factor Xa in the prothrombinase complex also renders it resistant to inhibition by exogenous heparin therapy which also requires antithrombin III to elicit its anticoagulant effect.
Thrombin is the primary mediator of thrombus formation. Thrombin acts directly to cause formation of insoluble fibrin from circulating fibrinogen. In addition, thrombin activates the zymogen factor XIII to the active transglutaminase factor XIIIa which acts to covalently stabilize the growing thrombus by crosslinking the fibrin strands. Lorand, L. and Konishi, K., Arch. Biochem. Biophys., 105:58 (1964). Beyond its direct role in the formation and stabilization of fibrin rich clots, the enzyme has been reported to have profound bioregulatory effects on a number of cellular components within the vasculature and blood. Shuman, M. A., Ann. NY Acad. Sci., 405:349 (1986).
It is believed that thrombin is the most potent agonist of platelet activation, and it has been demonstrated to be the primary pathophysiologic-mediator of platelet-dependent arterial thrombus formation. Edit, J. F. et al., J. Clin. Invest., 84:18 (1989). Thrombin-mediated platelet activation leads to ligand-induced inter-platelet aggregation principally due to the bivalent interactions between adhesive ligands such as fibrinogen and fibronectin with platelet integrin receptors such as glycoprotein IIb/IIIa which assume their active conformation following thrombin activation. Berndt, M. C. and Phillips, D. R., Platelets in Biology and Pathology, pp. 43-74, Elsevier/North Holland Biomedical Press (Gordon, J. L. edit. 1981). Thrombin-activated platelets can also support further thrombin production through the assembly of new prothrombinase and tenase (factor IXa, factor VIIIa and factor X) catalytic complexes on the membrane surface of intact activated platelets and platelet-derived microparticles, following thrombin-mediated activation of the non-enzymatic cofactors V and VIII, respectively. Tans, G. et al., Blood, 77:2641 (1991). This positive feedback process results in the local generation of large concentrations of thrombin within the vicinity of the thrombus which supports further thrombus growth and extension. Mann, K. G. et al., Blood, 76:1 (1990).
In contrast to its prothrombotic effects, thrombin has been shown to influence other aspects of hemostasis. These include its effect as an important physiological anticoagulant. The anticoagulant effect of thrombin is expressed following binding of thrombin to the endothelial cell membrane glycoprotein, thrombomodulin. This is thought to result in an alteration of the substrate specificity of thrombin thereby allowing it to recognize and proteolytically activate circulating protein C to give activated protein C (aPC). Musci, G. et al., Biochemistry, 27:769, (1988). aPC is a serine protease which selectively inactivates the non-enzymatic co-factors Va and VIIIa resulting in a down-regulation of thrombin formation by the prothrombinase. and tenase catalytic complexes, respectively. Esmon, C. T., Science, 235:1348 (1987). The activation of protein C by thrombin in the absence of thrombomodulin is poor.
Thrombin has also been shown to be a potent direct mitogen for a number of cell types, including cells of mesenchymal, origin such as vascular smooth muscle cells. Chen, L. B. and Buchanan, J. M., Proc. Natl. Acad. Sci. USA, 72:131 (1975). The direct interaction of thrombin with vascular smooth muscle also results in vasoconstriction. Walz, D. A. et al., Proc. Soc. Expl. Biol. Med., 180:518 (1985). Thrombin acts as a direct secretagogue inducing the release of a number of bioactive substances from vascular endothelial cells including tissue plasminogen activator. Levin, E. G. et al., Thromb. Haemost., 56:115 (1986). In addition to these direct effects on vascular cells, the enzyme can indirectly elaborate potent mitogenic activity on vascular smooth muscle cells by the release of several potent growth factors (e.g. platelet-derived growth factor, PDGF, and epidermal growth factor, EGF) from platelet xcex1-granules following thrombin-induced activation. Ross, R., N. Engl. J. Med., 314:408 (1986).
Many significant disease states are related to abnormal hemostasis. With respect to the coronary arterial vasculature, abnormal thrombus formation due to the rupture of an established atherosclerotic plaque is the major cause of acute myocardial infarction and unstable angina. Moreover, treatment of an occlusive coronary thrombus by either thrombolytic therapy or percutaneous transluminal coronary angioplasty (PTCA) is often accompanied by an acute thrombotic reclosure of the affected vessel which requires immediate resolution. With respect to the venous vasculature, a high percentage of patients undergoing major surgery in the lower extremities or the abdominal area suffer from thrombus formation in the venous vasculature which can result in reduced blood flow to the affected extremity and a predisposition to pulmonary embolism. Disseminated intravascular coagulopathy commonly occurs within both vascular,systems during septic shock, certain viral infections and cancer and is characterized by the rapid consumption of coagulation factors and systemic coagulation which results in the formation of life-threatening thrombi occurring throughout the vasculature leading to widespread organ failure.
Pathogenic thrombosis in the arterial vasculature is a major clinical concern in today""s medicine. It is the leading cause of acute myocardial infarction which is one of the leading causes of death in the western world. Recurrent arterial thrombosis also remains one of the leading causes of failure following enzymatic or mechanical recanalization of occluded coronary vessels using thrombolytic agents or percutaneous transluminal coronary angioplasty (PTCA), respectively. Ross, A. M., Thrombosis in Cardiovascular Disorder, p. 327, W. B. Saunders Co. (Fuster, V. and Verstraete, M. edit. 1991); Califf, R. M. and Willerson, J. T., id. at p 389. In contrast to thrombotic events in the venous vasculature, arterial thrombosis is the result of a complex interaction between fibrin formation resulting from the blood coagulation cascade and cellular components, particularly platelets, which make up a large percentage of arterial thrombi. Heparin, the most widely used clinical anticoagulant administered i.v., has not been shown to be universally effective in the treatment or prevention of acute arterial thrombosis or rethrombosis. Prins, M. H. and Hirsh, J., J. Am. Coll. Cardiol., 67:3A (1991).
Besides the unpredictable, recurrent thrombotic reocclusion which commonly occurs following PTCA, a profound restenosis of the recanalized vessel occurs in 30 to 40% of patients 1 to 6 months following this procedure. Califf, R. M. et al., J. Am. Coll. Cardiol., 17:2B (1991). These patients require further treatment with either a repeat PTCA or coronary artery bypass surgery to relieve the newly formed stenosis. Restenosis of a mechanically damaged vessel is not a thrombotic process but instead is the result of a hyperproliferative response in the surrounding smooth muscle cells which over time results in a decreased luminal diameter of the affected vessel due to increased muscle mass. Id. As for arterial thrombosis, there is currently no effective pharmacologic treatment for the prevention of vascular restenosis following mechanical recanalization.
The need for safe and effective therapeutic anticoagulants has in one aspect focused on the role of the serine protease thrombin in blood coagulation.
Most preferred natural substrates for thrombin are reported to contain an uncharged amino acid in the P3 recognition subsite. For example, the thrombin cleavage site on the Aa chain of fibrinogen, which is the primary physiological substrate for thrombin, is reported to contain a glycine residue in this position while the cleavage site on the Bb chain contains a serine, as shown below:
Peptidyl derivatives having an uncharged residue in the P3 position are said to bind to the active site of thrombin and thereby inhibit the conversion of fibrinogen to fibrin and cellular activation have been reported. These derivatives have either an aldehyde, chloromethyl. ketone or boronic acid functionality associated with the P1 amino acid. For example, substrate-like peptidyl derivatives such as D-phenylalanyl-prolyl-argininal (D-Phe-Pro-Arg-al), D-phenylalanyl-prolyl-arginine-chloromethyl ketone (P-PACK) and acetyl-D-phenylalanyl-prolyl-boroarginine (Ac-(D-Phe)-Pro-boroArg) have been reported to inhibit thrombin by directly binding to the active site of the enzyme. Bajusz, S., Symposia Biologica Hungarica, 25:277 (1984); Bajusz, S. et al., J. Med. Chem. 33:1729 (1990); Bajusz, S. et al., Int. J. Peptide Protein Res. 12:217 (1970); Kettner, C. and Shaw, E., Methods Enzymol., 80:826 (1987); Kettner, C. et al., EP 293,881 (published Dec. 7, 1988); Kettner, C., et al., J. Biol. Chem., 265:18209 (1990). These molecules have been reported to be potent anticoagulants in the prevention of platelet-rich arterial thrombosis. Kelly, A. B. et al., Thromb. Haemostas., 65:736 at abstract 257 (1991). Other peptidyl aldehydes have been proposed or reported as inhibitors of thrombin. See, e.g., Bey, P. et al., EP 363,284 (published Apr. 11, 1990) and Balasubramanian, N. et al., EP 526,877 (published Feb. 10, 1993).
Peptidyl compounds which are said to be active site inhibitors of thrombin but which differ in structure from those containing an uncharged amino acid in the P3 recognition subsite have been reported.
The compound, Argatroban (also called 2R,4R-4-methyl-1-[N-2-(3-methyl-1,2,3,4-tetrahydro-8-quinolinesulfonyl)-L-argininyl]-2-piperdinecarboxylic acid), is also reported to bind directly to the active site of thrombin and has been thought to be the most potent and selective compound in the class of non-peptidyl inhibitors of this enzyme. Okamoto, S. et al., Biochem. Biophys. Res. Commun., 101:440 (1981). Argatroban has been reported to be a potent antithrombotic agent in several experimental models of acute arterial thrombosis. Jang, I. K. et al., in both Circulation, 81:219 (1990) and Circ. Res., 67:1552 (1990).
Peptidyl compounds which are said to be inhibitors of thrombin and whose:mode of action is thought to be by binding to both the active site and another site on the enzyme have been reported. Hirudin and certain peptidyl derivatives of hirudin have been reported to inhibit both conversion of fibrinogen to fibrin and platelet activation by binding to either both the active site and exo site, or the exo site only, of thrombin. Markwardt, F., Thromb. Haemostas., 66:141 (1991). Hirudin is reported to be a 65 amino acid polypeptide originally isolated from leech salivary gland extracts. It is said to be one of the most potent inhibitors of thrombin known. Marki, W. E. and Wallis, R. B., Thromb. Haemostas., 64:344 (1990). It has been reported to inhibit thrombin by binding to both its anion-binding exo-site and to its catalytic active site which are distinct and physically distant from each other. Rydel, T. J. et al., Science, 249:277 (1990). Hirudin has been reported to be a potent antithrombotic agent in vivo. Markwardt, F. et al., Pharmazie, 43:202 (1988); Kelly, A. B. et al., Blood, 77:(1991). In addition to its antithrombotic effects, hirudin has been reported to also effectively inhibit smooth muscle proliferation and the associated restenosis following mechanical damage to an atherosclerotic rabbit femoral artery. Sarembock, I. J. et al., Circulation, 84:232 (1991).
Hirugen has been reported to be a peptide derived from the anionic carboxy-terminus of hirudin. It is reported to bind only to the anion binding exo-site of thrombin and thereby inhibit the formation of fibrin but not the catalytic turnover of small synthetic substrates which have access to the unblocked active site of the enzyme. Maraganore, J. M. et al., J. Biol. Chem., 264:8692 (1989); Naski, M. C. et al., J. Biol. Chem., 265:13484 (1990). The region of hirudin represented by hirugen has been reported, as according to by x-ray crystallographic analysis, to bind directly to the exo site of thrombin. Skrzypczak-Jankun, E. et al., Thromb. Haemostas., 65:830 at abstract 507 (1991). Moreover, the binding of hirugen has also been reported to enhance the catalytic turnover of certain small synthetic substrates by thrombin, indicating that a conformational change in the enzyme active site may accompany occupancy of the exo-site. Liu, U. W. et al., J. Biol. Chem., 266:16977 (1991). Hirugen also is reported to block thrombin-mediated platelet aggregation. Jakubowski, J. A. and Maraganore, J. M., Blood, 75:399 (1990).
A group of synthetic chimeric molecules comprised of a hirugen-like sequence linked by a glycine-spacer region to the peptide, D-phenylalanyl-prolyl-arginine, which is based on a preferred substrate recognition site for thrombin, has been termed to be hirulog. Maraganore et al., U.S. Pat. No. 5,196,404 (Mar. 23, 1993). The hirugen-like sequence is said to be linked to this peptide through the C-terminal end of the peptide. Maraganone, J. M. et al., Biochemistry, 29:7095 (1990). The hirulogs have been reported to be an effective antithrombotic agents in preventing both fibrin-rich and platelet-rich thrombosis. Maraganone, J. M. et al., Thromb. Haemostas., 65:651 at abstract 17 (1991).
Certain benzamidines have been reported to inhibit thrombin though non-selectively. 4-amidinophenylpyruvic acid (APPA) has been reported to be a thrombin inhibitor with low toxicity and favorable pharmacokinetics. However, this compound was reported to be non-selective, inhibiting trypsin, plasmin and kallikrein. Markwardt et al., Thromb. Res., 1:243-52 (1972). Other benzamidine-derived structures which have been reported to inhibit thrombin include the cyclic amides of Nxcex1-substituted 4-amidinophenylalanine and 2-amino-5-(4-amidinophenyl)-1-valeric acid. The inhibitory constant displayed by these compounds was reported to be in the micromolar range. Markwardt et al., Thromb. Res., 17:425-31 (1980). Moreover, derivatives of 4-amidinophenylalanine whose xcex1-amino group is linked to the arylsulfonyl residue via a xcfx89-aminoalkylcarboxylic acid as spacer have also been assessed for their inhibitory effect. Among these Nxcex1-(2-naphthylsulphonylglycyl)-4-amidino-phenylalanine piperidide (a-NAPAP) has been reported to possess an affinity for thrombin (Ki=6xc3x9710xe2x88x929 M). Banner et al., J. Biol. Chem., 266:20085 (1991) and Sturzebecher et al., Thromb. Res., 29:635-42 (1983).
Certain bis-benzamidines have been reported to inhibit thrombin. The antithrombin activity of bis-benzamidines was reported to increase with the length and bulkiness of the central chain. However, these compounds were reported to be generally toxic in the micromolar range where they are also inhibitory. Geratz et al., Thromb. Diath. Haemorrh., 29:154-67 (1973); Geratz et al., J. Med. Chem., 16:970-5 (1973); Geratz et al., J. Med. Chem., 19:634-9 (1976); Walsmann et al., Acta Biol. Med. Germ., 35:K1-8 (1976); and Hauptmann et al., Acta Biol. Med. Germ., 35:635-44 (1976).
Certain amidino-bearing aromatic ring structures such as xcex2-naphthamidines have been reported to possess modest antithrombin and anticoagulant activity. This class of compounds include the non-selective 6-amidino-2-naphthyl-4-guanidinobenzoate dimethanesulfonate (FUT 175). Fuji et al., Biochim. Biophys. Acta, 661:342-5 (1981); and Hitomi et al., Haemostasis, 15:164-8 (1985).
Certain phenylguanidines have been reported to inhibit thrombin. Derivatives of 4-guanidinophenylalanine with inhibitory constants in the micromolar range have been reported to inhibit thrombin. This class includes the Nxcex1-tosylated and dansylated 4-guanidino phenylalanine piperidides. Claeson et al., Thromb. Haemostas., 50:53 (1983). Another compound, [ethyl p-(6-guanidinohexanoyloxy)benzoate]methane sulfonate (FOY) was reported to be a non-selective competitive inhibitor of thrombin. Ohno et al., Thromb. Res., 19:579-588 (1980).
Certain compounds having inhibitory activity toward serine proteases, including thrombin, factor Xa, and trypsin, are disclosed within the following commonly assigned United States patents or published PCT applications: U.S. Pat. Nos. 5,371,072; 5,492,895; 5,534,498; 5,597,804; 5,637,599; 5,646,165; 5,656,600; 5,656,645; WO 94/13693; WO 95/35311; WO 95/35313; WO 96/19493.
Substances which interfere in the process of blood coagulation (anticoagulants) have been demonstrated to be important therapeutic agents in the treatment and prevention of thrombotic disorders (Kessler, C. M. (1991) Chest 99: 97S-112S and Cairns, J. A., Hirsh, J., Lewis, H. D., Resnekov, L., and Theroux, P. (1992) Chest 102: 456S-481S). The currently approved clinical anticoagulants have been associated with a number of adverse effects owing to the relatively non-specific nature of their effect on the blood coagulation cascade (Levine, M. N., Hirsh, J., Landefeld, S., and Raskob, G. (1992) Chest 102: 352S-363S). This has stimulated the search for more effective anticoagulant agents which can more effectively control the activity of the coagulation cascade by selectively interfering with specific reactions in this process which may have a positive effect in reducing the complications of anticoagulant therapy (Weitz, J., and Hirsh, J. (1993) J. Lab. Clin. Med. 122:364-373). In another aspect, this search has focused on normal human proteins which serve as endogenous anticoagulants in controlling the activity of the blood coagulation cascade. In addition, various hematophageous organisms have been investigated because of their ability to effectively anticoagulate the blood meal during and following feeding on their hosts suggesting that they have evolved effective anticoagulant strategies which may be useful as therapeutic agents.
The present invention is directed to novel compounds having a lactam at P3 and at P1 have a six membered heterocyclic ring having two nitrogen atoms and the remainder of the ring atoms carbon atoms. These compounds are potent inhibitors of thrombin.
Thus, according to one aspect, the present invention is directed to compounds of the formula (I):
R1xe2x80x94X-Lac-Jxe2x80x94Exe2x80x83xe2x80x83(I)
wherein
(a) X is selected from the group consisting of xe2x80x94S(O)2xe2x80x94, xe2x80x94N(Rxe2x80x2)xe2x80x94S(O)2xe2x80x94, xe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94OC(xe2x95x90O)xe2x80x94, xe2x80x94N(Rxe2x80x2)C(xe2x95x90O)xe2x80x94, and a direct link, wherein Rxe2x80x2 is selected from hydrogen, alkyl of 1 to about 4 carbon atoms, aryl of about 6 to about 14 carbon atoms and aralkyl of about 6 to about 16 carbon atoms;
(b) R1 is selected from the group consisting of:
(1) alkyl of 1 to about 12 carbon atoms which is optionally substituted with Y1 and/or Y2,
(2) alkyl of 1 to about 3 carbon atoms substituted with cycloalkyl of about 3 to about 8 carbon atoms which is optionally mono-, di-, or tri-substituted on the ring with Y1, Y2 and/or Y3,
(3) cycloalkyl of 3 to about 15 carbon atoms, which is optionally mono-, di-, or tri-substituted on the ring with Y1, Y2 and/or Y3,
(4) heterocycloalkyl of 4 to about 10 ring atoms with the ring atoms selected from carbon and heteroatoms, wherein the heteroatoms are selected from the group consisting of oxygen, nitrogen, and S(O)i, wherein i is 0, 1 or 2, which is optionally mono-, di-, or tri-substituted on the ring with Y1, Y2 and/or Y3,
(5) heterocyclo of 4 to about 10 ring atoms with the ring atoms selected from carbon and heteroatoms, wherein the heteroatoms are selected from the group consisting of oxygen, nitrogen, and S(O)i, including 
xe2x80x83wherein 
xe2x80x83is a 5 to 7 member heterocycle of 3 to 6 ring carbon atoms, where G is xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94S(xe2x95x90O)xe2x80x94, xe2x80x94S(O)2xe2x80x94 or xe2x80x94Sxe2x80x94, which is optionally mono-, di-, or tri-substituted on the ring carbons with Y1, Y2 and/or Y3,
(6) alkenyl of about 2 to about 6 carbon atoms which is optionally substituted with cycloalkyl of about 5 to about 8 carbon atoms, which is optionally mono-, di-, or tri-substituted on the ring carbons with Y1, Y2 and/or Y3,
(7) aryl of about 6 to about 14 carbon atoms which is optionally mono-, di- or tri-substituted with Y1, Y2, and/or Y3,
(8) heteroaryl of about 5 to about 14 ring atoms with the ring atoms selected from carbon and heteroatoms, wherein the heteroatoms are selected from oxygen, nitrogen, and sulfur, and which is optionally mono-, di-, or tri-substituted with Y1, Y2, and/or Y3,
(9) aralkyl of about 7 to about 15 carbon atoms which is optionally substituted on the alkyl chain with hydroxy or halogen and mono-, di-, or tri-substituted in the aryl ring with Y1, Y2, and/or Y3,
(10) heteroaralkyl of 5 to 14 ring atoms with the ring atoms selected from carbon and heteroatoms, wherein the heteroatoms are selected from oxygen, nitrogen, and sulfur, and which is optionally substituted on the alkyl chain with hydroxy or halogen and optionally mono-, di- or tri-substituted on the ring with Y1, Y2, and/or Y3,
(11) aralkenyl of about 8 to about 16 carbon atoms which is optionally mono-, di-, or tri-substituted on the aryl ring with Y1, Y2, and/or Y3,
(12) heteroaralkenyl of 5 to 14 ring atoms with the ring atoms selected from carbon and heteroatoms, wherein the heteroatoms are selected from oxygen, nitrogen, and sulfur, and which is optionally mono-, di- or tri-substituted on the ring with Y1, Y2, and/or Y3, 
(17) fused carbocyclic alkyl of about 5 to about 15 carbon atoms,
(18) difluoromethyl or perfluoroalkyl of 1 to about 12 carbon atoms,
(19) perfluoroaryl of about 6 to about 14 carbon atoms,
(20) perfluoraralkyl of about 7 to about 15 carbon atoms, and
(21) hydrogen when X is a direct link;
xe2x80x83wherein
(i) each Y1, Y2, and Y3 is independently selected from the group consisting of halogen, cyano, nitro, tetrazolyl optionally substituted with alkyl of 1 to about 6 carbon atoms, guanidino, amidino, methylamino, methylguanidino, xe2x80x94CF3, xe2x80x94CF2CF3, xe2x80x94CH(CF3)2, xe2x80x94C(OH)xe2x80x94(CF3)2, xe2x80x94OCF3, xe2x80x94OCF2CF3, xe2x80x94OCF2H, xe2x80x94OC(O)NH2, xe2x80x94OC(O)NHZ1, xe2x80x94OC(O)NZ1Z2, xe2x80x94NHC(O)Z1, xe2x80x94NHC(O)NH2, xe2x80x94NHC(O)NHZ1, xe2x80x94NHC(O)NZ1Z2, xe2x80x94C(O)OH, xe2x80x94C(O)OZ1, xe2x80x94C(O)NH2, xe2x80x94C(O)NZ1Z2, xe2x80x94P(O)3H2, xe2x80x94P(O)3(Z1)2, xe2x80x94S(O)3H, xe2x80x94S(O)pZ1, xe2x80x94Z1, xe2x80x94OZ1, xe2x80x94OH, xe2x80x94NH2, xe2x80x94NHZ1, xe2x80x94NZ1Z2, N-morpholino, and xe2x80x94S(O)p(CF2)qCF3, wherein p is 0, 1 or 2, q is an integer from 0 to 5, and Z1 and Z2 are independently selected from the group consisting of alkyl of 1 to about 12 carbon atoms, aryl of about 6 to about 14 carbon atoms, heteroaryl of about 5 to about 14 atoms having 1 to about 9 carbon atoms, aralkyl of about 7 to about 15 carbon atoms, and heteroaralkyl of about 5 to about 14 ring atoms having about 3 to about 9 carbon atoms, or
(ii) Y1 and Y2 are selected together to be xe2x80x94O[C(Z3)(Z4)]rOxe2x80x94 or xe2x80x94O[C(Z3)(Z4)]r+1xe2x80x94, wherein r is an integer from 1 to 4 and Z3 and Z4 are independently selected from the group consisting of hydrogen, alkyl or 1 to about 12 carbon atoms, aryl of about 6 to about 14 carbon atoms, heteroaryl of about 5 to about 14 ring atoms having 1 to about 9 carbon atoms, aralkyl of about 7 to about 15 carbon atoms, and heteroaralkyl of about 5 to about 14 ring atoms having about 3 to about 9 carbon atoms;
(c) Lac is selected from the group consisting of 
xe2x80x83wherein
(i) n is 0, 1, 2, or 3; and
(ii) R2 and R3 are independently selected from the group consisting of hydrogen, alkyl of 1 to about 6 carbon atoms, cycloalkyl of 3 to about 8 carbon atoms, and aryl of about 6 to about 14 carbon atoms or R2 and R3 taken together are CH2; and
(d) J is selected from 
wherein R4 is selected from the group consisting of hydrogen, alkyl of 1 to about 6 carbon atoms; cycloalkyl of 3 to about 8 carbon atoms and aryl of about 6 to about 14 carbon atoms; R5a and R5b are independently selected from hydrogen, fluoro, chloro and alkyl of 1 to about 3 carbon atoms; R6 is hydrogen, alkyl of 1 to about 3 carbon atoms, xe2x80x94C(xe2x95x90O)R7a, or xe2x80x94CH2OR7b; R7a is alkyl of 1 to about 6 carbon atoms, alkoxy of 1 to about 6 carbon atoms, amino, alkylamino of 1 to about 6 carbon atoms or dialkylamino of 2 to about 12 carbon atoms; R7b is hydrogen, acyl, or alkyl of 1 to about 6 carbon atoms; and Q7, Q8 and Q9 are independently selected from C(R5a), N, S and O, provided that (i) Q7, Q8 and Q9 are not all C(R5a) and (ii) only one of Q7, Q8 and Q9 can be O or S;
(e) alternatively Lac-J is 
wherein m is 1, 2 or 3 and J1 is xe2x80x94C(xe2x95x90O)xe2x80x94NHxe2x80x94CH2xe2x80x94; and
(f) E is a six membered heterocyclic ring having two ring nitrogen atoms and the remainder of the ring atoms carbon atoms which is substituted with 
xe2x80x83on a ring carbon and is substituted with R10 and R11 on different ring carbons wherein
(1) R8 is selected from hydrogen, alkyl of about 1 to about 4 carbon atoms, cycloalkyl of 3 to about 7 carbon atoms, xe2x80x94(CF2)kCF3, xe2x80x94OR12 and xe2x80x94C(xe2x95x90O)R12 wherein R12 is hydrogen, alkyl of 1 to about 4 carbon atoms and k is 0, 1, 2 or 3;
(2) R9 is selected from hydrogen and alkyl of 1 to about 4 carbon atoms;
(3) alternatively R8 and R9 are taken together to give a divalent radical of the formula xe2x80x94(CH2)wxe2x80x94 wherein w is 3, 4 or 5; and
(4) R10 and R11 are independently selected from hydrogen, alkyl of 1 to about 4 carbon atoms, alkyl of 1 to about 4 carbon atoms substituted with alkoxy of 1 to about 3 carbon atoms, alkoxy of 1 to about 8 carbon atoms, halogen, trifluoromethyl, xe2x80x94OC(R13)(R14)xe2x80x94C(xe2x95x90O)xe2x80x94R15 wherein R13 and R14 are independently selected from hydrogen or alkyl of 1 to about 4 carbon atoms, R15 is hydroxy, alkoxy of 1 to about 4 carbon atoms or xe2x80x94N(R16)(R17) wherein R16 and R17 are independently hydrogen or alkyl of 1 to about 4 carbon atoms;
and pharmaceutically acceptable salts thereof.
In one aspect, the present invention is directed to compounds which are potent inhibitors of thrombin. According to a preferred aspect, these compounds comprise novel azepin-2-one peptidomimetics. The present invention is also directed to pharmaceutical compositions which comprise one of these compounds and a pharmaceutically acceptable carrier. These compounds and pharmaceutical compositions are potent inhibitors of blood coagulation in vitro and in vivo in mammals. These compounds and pharmaceutical compositions may be used as therapeutic agents for treating disease states in mammals which are characterized by abnormal thrombosis. A further aspect of the present invention is directed to the use of these compounds and pharmaceutical compositions for treatment of disease states in mammals characterized by abnormal thrombosis. An alternate aspect of the present invention is directed to methods of using these thrombin inhibitors as in vitro diagnostic agents.
In yet another aspect, the present invention is directed to methods of using the compounds and pharmaceutical compositions of the present invention for the prevention of thrombosis in a mammal suspected of having a condition characterized by abnormal thrombosis, comprising administering to said mammal a therapeutically effective amount of a compound of the present invention or pharmaceutical composition comprising such a compound.
In accordance with the present invention and as used herein, the following terms are defined to have following meanings, unless explicitly stated otherwise:
In referring to formula (I), P1, P2, P3 and P4 denote the portions of the molecule indicated below: 
wherein R1, X, Lac, J and E are as defined in connection with formula (I).
The term xe2x80x9cacylxe2x80x9d refers to the group xe2x80x94C(xe2x95x90O)Rxe2x80x2 where Rxe2x80x2 is a hydrocarbyl group.
The term xe2x80x9calkenylxe2x80x9d refers to unsaturated aliphatic groups having at least one double bond.
The term xe2x80x9calkynylxe2x80x9d refers to unsaturated aliphatic groups having at least one triple bond.
The term xe2x80x9calkylxe2x80x9d refers to saturated aliphatic groups including straight-chain, branched-chain and cyclic groups.
The terms xe2x80x9calkoxyxe2x80x9d and xe2x80x9calkoxylxe2x80x9d refer to a group having the formula, Rxe2x80x94Oxe2x80x94, wherein R is an alkyl group.
The term xe2x80x9calkoxycarbonylxe2x80x9d refers to xe2x80x94C(O)OR wherein R is alkyl.
The term xe2x80x9caminoalkylxe2x80x9d refers to an alkyl group substituted with an amino (NH2) group.
The term xe2x80x9caralkenylxe2x80x9d refers to an alkenyl group substituted with an aryl group. Preferably the alkenyl group has from 2 to about 6 carbon atoms.
The term xe2x80x9caralkylxe2x80x9d refers to an alkyl group substituted with an aryl group. Suitable aralkyl groups include benzyl, picolyl, and the like, all of which may be optionally substituted. Preferably the alkyl group has from 1 to about 5 carbon atoms.
The term xe2x80x9carylxe2x80x9d refers to an aromatic group which has at least one ring having a conjugated pi electron system and includes a carbocyclic aryl, heterocyclic aryl and biaryl groups, all of which may be optionally substituted.
The term xe2x80x9caryloxyxe2x80x9d refers to a group having the formula, Rxe2x80x94Oxe2x80x94, wherein R is an aryl group.
The term xe2x80x9caryloxyxe2x80x9d refers to a group having the formula, Rxe2x80x94Oxe2x80x94, wherein R is an aralkyl group.
The term xe2x80x9camino acidxe2x80x9d refers to both natural and unnatural amino acids in their D and L stereoisomers, if their structures allow such stereoisomeric forms, and their analogs. Natural amino acids include alanine (Ala), arginine (Arg), asparagine (Asn), aspartic acid (Asp), cysteine (Cys), glutamine (Gln), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan (Trp), tyrosine (Tyr) and valine (Val). Unnatural amino acids include, but are not limited to, azetidinecarboxylic acid, 2-aminoadipic acid, 3-aminoadipic acid, beta-alanine, aminopropionic acid, 2-aminobutyric acid, 4-aminobutyric acid, 6-aminocaproic acid, 2-aminoheptanoic acid, 2-aminoisobutyric acid, 3-aminoisobutyric acid, 2-aminopimelic acid, 2,4 diaminoisobutyric acid, demosine, 2,2xe2x80x2-diaminopimelic acid, 2,3-diaminopropionic acid, N-ethylglycine, N-ethylasparagine, hydroxylysine, allo-hydroxylysine, 3-hydroxyproline, 4-hydroxyproline, isodesmosine, allo-isoleucine, N-methylglycine, N-methylisoleucine, N-methylvaline, norvaline, norleucine, ornithine and pipecolic acid. Amino acid analogs include the natural and unnatural amino acids which are chemically blocked, reversibly or irreversibly, or modified on their N-terminal amino group or their side-chain groups, as for example, methionine sulfoxide, methionine sulfone, S-(carboxymethyl)-cysteine, S-(carboxymethyl)-cysteine sulfoxide and S-(carboxymethyl)-cysteine sulfone.
The term xe2x80x9camino-acid residuexe2x80x9d refers to radicals having the structure: (1) xe2x80x94C(O)xe2x80x94Rxe2x80x94NHxe2x80x94, wherein R typically is xe2x80x94CH(Rxe2x80x2)xe2x80x94, wherein Rxe2x80x2 is H or a carbon containing substituent; or (2) 
wherein p is 1, 2 or 3 representing the azetidinecarboxylic acid, proline or pipecolic acid residues, respectively.
The term xe2x80x9camino acid analogxe2x80x9d refers to an amino acid wherein either the C-terminal carboxy group, the N-terminal amino group or side-chain functional group has been chemically modified to another functional group. For example, aspartic acid-(beta-methyl ester) is an amino acid analog of aspartic acid; N-ethylglycine is an amino acid analog of glycerine; or alanine carboxamide is an amino acid analog of alanine.
xe2x80x9cArginine mimic side chainxe2x80x9d or xe2x80x9cside chain of an arginine mimicxe2x80x9d refers to a group of atoms which spatially and electronically resemble or mimic the normal arginine side chain. These groups include the cyclic R5 groups defined in connection with formula (I).
xe2x80x9cBiarylxe2x80x9d refers, to phenyl substituted by carbocyclic or heterocyclic aryl as defined herein, ortho, meta or para to the point of attachment of the phenyl ring.
xe2x80x9cBrinexe2x80x9d refers to an aqueous saturated solution of sodium chloride.
xe2x80x9cCamphor derivativexe2x80x9d refers to the groups: 
xe2x80x9cCarbocyclicxe2x80x9d refers to a group having one or more rings wherein the ring atoms are all carbon atoms and includes groups having aryl, cycloalkyl, and unsaturated cycloalkyl or a combination of such rings. Such groups include cyclohexyl, cycloheptenyl, tetrahydronaphthyl, phenyl, naphthyl, and the like.
xe2x80x9cCarbocyclic arylxe2x80x9d refers to aromatic groups wherein the ring atoms on the aromatic ring are carbon atoms. Carbocyclic aryl groups include monocyclic carbocyclic aryl groups and naphthyl groups, all of which may be optionally substituted. Suitable carbocyclic aryl groups include phenyl and naphthyl. Suitable substituted carbocyclic aryl groups include indene and phenyl substituted by one to two substituents such being advantageously lower alkyl, hydroxy, lower alkoxy, lower alkoxycarbonyl, halogen, trifluoromethyl, nitro, and cyano. Substituted naphthyl refers to 1- or 2-naphthyl substituted by lower alkyl, lower alkoxy, or halogen.
xe2x80x9cCarboxylate mimicxe2x80x9d or xe2x80x9ccarboxylic acid mimicxe2x80x9d refers to a group which spatially and electronically mimics a carboxylic acid and provides a net negative charge, i.e., an anion, and also has a pKa value similar to that of a corresponding carboxylic acid, preferably having a pKa of about 4 to 5.
xe2x80x9cCycloalkenylxe2x80x9d or xe2x80x9cunsaturated cycloalkylxe2x80x9d refers to a cyclic alkenyl group, that is, a cycloalkyl group modified by having at least one double band. Suitable cycloalkenyl groups include, for example, cyclopentenyl and cyclohexenyl.
xe2x80x9cCycloalkylxe2x80x9d refers to a cyclic alkyl group. Suitable cycloalkyl groups include, for example, cyclohexyl, cyclopropyl, cyclopentyl, and cycloheptyl.
xe2x80x9cCyclohexylmethylxe2x80x9d refers to a cyclohexyl group attached to CH2.
xe2x80x9cFused carbocyclicxe2x80x9d refers to a group having multiple rings which are fused, including multicyclic fused carbocyclic rings having both aromatic and non-aromatic rings. Suitable fused carbocyclic rings include fluorenyl, tetralin and the like.
xe2x80x9cFused carbocyclic alkylxe2x80x9d refers to an alkyl group substituted with a fused carbocyclic ring moiety, preferably a multicyclic fused carbocyclic ring having both aromatic and nonaromatic rings. Suitable fused carbocyclic alkyl groups include fluorenyl methyl and the like.
The term xe2x80x9chalogenxe2x80x9d refers to fluorine, chlorine, bromine and iodine.
xe2x80x9cHeterocyclicxe2x80x9d refers to a group having 1 or more rings wherein the ring atoms are carbon atoms or heteroatoms, and includes rings that are reduced, saturated, unsaturated and aromatic and, if the group has more than one ring, includes a combination of such rings. Suitable heteroatoms include oxygen, nitrogen and S(O)i wherein i is 0, 1 or 2. Thus, heterocyclic groups include groups having (i) heterocyclo rings (ii) unsaturated heterocyclo rings, (iii) heteroaryl rings or (iv) a combination of such rings.
xe2x80x9cHeteroarylxe2x80x9d refers to aromatic groups having a mixture of carbon atoms and heteroatoms. Preferred heteroaryl groups include those having 5 to 14 ring atoms and from 1 to 9 carbon atoms and the remainder of the ring atoms heteroatoms. Heteroaryl groups include those heterocyclic systems described in xe2x80x9cHandbook of Chemistry and Physicsxe2x80x9d, 49th edition, 1968, R. C. Weast, editor; The Chemical Rubber Co., Cleveland, Ohio. See particularly Section C, Rules for Naming Organic Compounds, B. Fundamental Heterocyclic Systems. Suitable heteroatoms include oxygen, nitrogen, and sulfur. Typical heteroaryl groups include furanyl, thienyl, pyridyl, pyrrolyl, pyrimidyl, pyrazinyl, imidazolyl, pyrazolyl, oxazolyl, thiazolyl and the like.
xe2x80x9cHeteroaralkenylxe2x80x9d refers to an alkenyl group substituted with a heteroaryl group. Preferably the alkenyl group has from 2 to about 6 carbon atoms.
xe2x80x9cHeteroaralkylxe2x80x9d refers to an alkyl group substituted with a heteroaryl group. Preferably the alkyl group has from 1 to about 6 carbon atoms.
xe2x80x9cHeterocycloxe2x80x9d refers to a reduced heterocyclic ring system comprised of carbon, nitrogen, oxygen and/or sulfur atoms, and includes such heterocyclic systems described in xe2x80x9cHandbook of Chemistry and Physicsxe2x80x9d, 49th edition, 1968, R. C. Weast, editor; The Chemical Rubber Co., Cleveland, Ohio. See particularly Section C, Rules for Naming Organic Compounds, B. Fundamental Heterocyclic Systems.
xe2x80x9cUnsaturated heterocycloxe2x80x9d refers to a heterocyclo group which is modified by having at least one double bond, but which is not aromatic.
xe2x80x9cHeterocycloalkylxe2x80x9d refers to an alkyl group substituted with a heterocyclo group. Preferably the alkyl group has from 1 to about 6 carbon atoms.
The term xe2x80x9chydrocarbylxe2x80x9d denotes an organic radical composed of carbon and hydrogen which may be aliphatic (including alkyl, alkenyl and alkynyl groups and groups which have a mixture of saturated and unsaturated bonds), alicyclic (such as cycloalkyl), aromatic (such as aryl) or combinations thereof, and may refer to straight-chained, branched-chain or to cyclic structures or to radicals having a combination thereof, as well as to radicals substituted with halogen atom(s) or heteroatoms, such as nitrogen, oxygen and sulfur and their functional groups (such as amino, alkoxy, aryloxy, lactone groups, and the like), which are commonly found in organic compounds and radicals.
The term xe2x80x9chydroxyalkylxe2x80x9d refers to an alkyl group substituted with a hydroxy group.
The term xe2x80x9clowerxe2x80x9d referred to herein in connection with organic radicals or compounds defines such with up to and including 6, preferably up to and including 4 and advantageously one or two carbon atoms. Such groups may be straight chain or branched chain.
xe2x80x9cPerfluoroalkylxe2x80x9d refers to an alkyl group which has every hydrogen replaced with fluorine.
xe2x80x9cPerfluoroarylxe2x80x9d refers to an aryl group which has every hydrogen replaced with fluorine.
xe2x80x9cPerfluoroarylalkylxe2x80x9d or xe2x80x9cPerfluoroaralkylxe2x80x9d refers an aralkyl group in which every hydrogen on the aralkyl moiety is replaced with fluorine.
xe2x80x9cPharmaceutically acceptable saltxe2x80x9d includes salts of the compounds of the present invention derived from the combination of such compounds and an organic or inorganic acid. In practice the use of the salt form amounts to use of the base form. The compounds of the present invention are useful in both free base and salt form, with both forms being considered as being within the scope of the present invention.
The term xe2x80x9cquaternary ammonium saltxe2x80x9d refers to compounds produced by reaction between a basic nitrogen in an R substituent and an alkylhalide, arylhalide, and aralkylhalide. Other reactants with good leaving groups may also be used, such as alkyl trifluoromethanesulfonates, alkyl methanesulfonates, and alkyl p-toluenesulfonates. A quaternary ammonium salt has a positively charged nitrogen in the R substituent. Pharmaceutically acceptable counterions include Clxe2x80x94, Brxe2x88x92, Ixe2x88x92, CF3C(O)Oxe2x88x92 and CH3C(O)Oxe2x88x92. The counterion of choice can be made using ion exchange resin columns. R groups with basic nitrogens include xe2x80x94CH2CH2CH2NHC(xe2x95x90NH)NH2, 
xe2x80x94(CH2)pNH2, wherein p is an integer from 1 to 6. For example, the following R groups contain basic nitrogens: 3-(R)-quinuclidine, 3-(S)-quinuclidine, 3-yl-2-ethyl-4(3H)-quinazolinone, ethyl morpholine, ethyl piperidine, 2-(2-ethyl)pyridine, and 4-(methyl)-5-hydroxy-6-methyl-3-pyridine methanol.
xe2x80x9cTrihydrocarbylsilylxe2x80x9d refers to the group 
wherein each R is an independently selected hydrocarbyl group.
The term xe2x80x9cterminal carbonxe2x80x9d refers to the carbon atom of a straight chain alkyl which is furthest from the parent structure.
In addition, the following abbreviations stand for the following:
xe2x80x9cBnxe2x80x9d refers to benzyl.
xe2x80x9cBocxe2x80x9d or xe2x80x9cBOCxe2x80x9d refers to t-butoxycarbonyl.
xe2x80x9cBoc2Oxe2x80x9d refers to Boc anhydride or di-tert-butyl dicarbonate.
xe2x80x9cBOPxe2x80x9d refers to benzotriazol-1-yl-oxy-tris-(dimethylamino)-phosphonium hexafluorophosphate.
xe2x80x9cBnSO2xe2x80x9d or xe2x80x9cBzlSO2xe2x80x9d refers to benzylsulfonyl.
xe2x80x9ct-BuOKxe2x80x9d refers: to potassium tert-butoxide.
xe2x80x9cCbzxe2x80x9d or xe2x80x9cCBzxe2x80x9d refers to benzyloxycarbonyl.
xe2x80x9cDCAxe2x80x9d refers to dichloroacetic acid.
xe2x80x9cDCCxe2x80x9d refers to N,Nxe2x80x2-dicyclohexylcarbodiimide.
xe2x80x9cDCExe2x80x9d refers to 1,2-dichloroethane.
xe2x80x9cDCMxe2x80x9d refers to dichloromethane (also called methylene chloride).
xe2x80x9cDHPxe2x80x9d refers to 3,4-dihydro-2H-pyran.
xe2x80x9cDMFxe2x80x9d refers to N,N-dimethylformamide.
xe2x80x9cDMSOxe2x80x9d refers to dimethyl sulfoxide.
xe2x80x9cDMAPxe2x80x9d refers to 4-N,N-dimethylamino-pyridine.
xe2x80x9cDPPAxe2x80x9d refers to diphenylphosphoryl azide.
xe2x80x9cEDACxe2x80x9d or xe2x80x9cEDCxe2x80x9d refers to 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide hydrochloride salt.
xe2x80x9cEt3Nxe2x80x9d refers to triethylamine.
xe2x80x9cEtOHxe2x80x9d refers to ethanol.
xe2x80x9cHATUxe2x80x9d refers to O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate.
xe2x80x9cHBTUxe2x80x9d refers to 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate.
xe2x80x9cHClxe2x80x9d refers to hydrochloric acid.
xe2x80x9cHOAcxe2x80x9d refers to acetic acid.
xe2x80x9cHOAtxe2x80x9d refers to 1-hydroxy-7-azabenzotriazole.
xe2x80x9cHOBtxe2x80x9d refers to 1-hydroxybenzotriazole monohydrate.
xe2x80x9cHPLCxe2x80x9d refers to high pressure liquid chromatography.
xe2x80x9cKOAcxe2x80x9d refers to potassium acetate.
xe2x80x9ci-BuOCOClxe2x80x9d refers to isobutyl chloroformate.
xe2x80x9cLiAlH4xe2x80x9d refers to lithium aluminum hydride.
xe2x80x9cLiAlH2(OEt)2xe2x80x9d refers to lithium diethoxy aluminum hydride.
xe2x80x9cMexe2x80x9d refers to methyl.
xe2x80x9cNaOHxe2x80x9d refers to sodium hydroxide.
xe2x80x9cNBSxe2x80x9d refers to N-bromosuccinimide.
xe2x80x9cNMMxe2x80x9d refers to N-methylmorpholine.
xe2x80x9cPh3Pxe2x80x9d or xe2x80x9cPPh3xe2x80x9d refers to triphenylphosphine.
xe2x80x9c2-PrPenxe2x80x9d refers to 2-propylpentanoyl.
xe2x80x9cpTSAxe2x80x9d or xe2x80x9cpTSA catalystxe2x80x9d refers to para-toluenesuflonic acid catalyst.
xe2x80x9cTBTUxe2x80x9d refers to 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate.
xe2x80x9cTEAxe2x80x9d refers to triethylamine.
xe2x80x9cTFAxe2x80x9d refers to trifluoroacetic acid.
xe2x80x9cTHFxe2x80x9d refers to tetrahydrofuran.
xe2x80x9cTLCxe2x80x9d refers to thin layer chromatography.